Custom CSS, reset and operational control
Apply area-specific CSS safely and understand exactly what Reset does and does not clear.
Guides in this workflow
Follow the guide that matches the exact action, filter, menu change or issue.
Add administrator-only custom CSS
Enter CSS in the administrator-area box and save.
Add client-only custom CSS
Enter CSS in the client-area box and save.
Add shared administrator and client CSS
Enter CSS in the combined box and save.
Understand custom CSS output
Stored CSS is inserted into a style element after line-break normalisation.
Apply custom CSS security controls
Only trusted administrators should enter CSS because it is injected into application pages.
Reset generated theme values
Use Reset to set theme_style to an empty JSON array.
Understand what Reset does not clear
Reset does not clear the three separately stored custom-CSS options.
Clear custom CSS explicitly
Remove content from all relevant CSS boxes and Save.
Test a theme change safely
Use a controlled browser/session and verify admin, client, login and external-form pages.